Define `toString` directly on Algorithm subclasses?

[lgarron]

Pros:

• Nice, concise formatting by default! (node actually truncates nested values)
• Can still convert to JSON, so inspectability is not lost.

Cons:

• Javascript does magic type conversion, and this could cause unexpected issues. For all I know 1 + [alg representing 2R] could turn into 3.
• Viewing the printed alg instead of the structure might hide unexpected discrepancies.